Not only is the free, open source KeePass (KeePassX for Mac users) a fantastic encrypted database to keep your passwords, it also does well to track your software licenses too.

Just create a new folder for software licenses, and enter the title and serial number in the notes area. You can add the download link to the URL field and even attach files (like the email the registration information arrived in) to the KeePass entry. If you haven't tried KeePass yet and you're sick of tracking passwords saved in 6 different Firefox installations, here's how to securely track your passwords with KeePass. Get started by importing your saved Firefox passwords into your KeePass database.